1. Field of the Invention
The present invention relates generally to liquid testing and more specifically to a sampling container for withdrawing liquid samples from various depths.
2. Brief Description of the Prior Art
Numerous devices have been proposed heretofore for the purpose of obtaining liquid samples for testing purposes. Typically such devices included a sampling container having a closure, means for lowering the container into the liquid and means for remotely actuating the closure to trap liquid in the container.
Many of these prior devices did not provide adequate versatility to meet conditions of particular applications. For example, these devices generally were designed for taking liquid samples over but a limited range of depths. U.S. Pat. Nos. 1,511,223 and 844,433 typified devices using rigid poles for the purpose of lowering the sampling container into a liquid body. The use of lengthy poles necessitated by certain applications resulted in a quite cumbersome procedure, and such devices therefore were deficient except for sampling near the surface.
Other sampling devices employed a rigid rod for the purpose of remotely actuating the container closure and as such suffered from the same limitations with regard to the adaptability for use over various depths.
A further approach toward sampling container design utilized a valve mechanism at the lower end of a container which was intended to permit the entrance of liquid into the container upon descent of the container. The valve mechanism was to seal the container to prevent the withdrawal of the liquid while the container was being lifted. It should be appreciated that, in addition to the disadvantages inherent in valve design and the numerous components employed in conjunction with such valves, these devices did not obtain true indicative samples from varying depths. This was due to the fact that liquid drawn into the bottom of the container on descent of the container tended to remain trapped in the container during further descent. Thus, the liquid samples obtained were not truly representative of the liquid at the depth to which the container was lowered.
Other sampling devices suffered from complexity of operation requiring difficult manipulation and dual controls--one for lowering the container and another for operating the closure.
As a result of the disadvantages of such prior sampling containers, these containers were generally designed for specific applications, e.g. oil tank sampling containers, such as U.S. Pat. Nos. 1,511,223 and 1,544,206, and did not provide adequate versatility for a wide range of applications.
In addition, virtually all liquid sampling containers of this type were designed for the purpose of retrieving a liquid sample which was then transferred to a breaker or other suitable container to proceed with the various tests to be conducted. This procedure inhibited immediate on site determinations, introduced additional sources of error, and required additional laboratory equipment to be used and cleansed.